In a radial turbine provided with a single turbine wheel that converts the swirling energy of a flow of swirling fluid, which flows into the turbine wheel with a flow velocity component in the radial direction serving as the main component thereof, into rotational motive power and that expels the flow, whose energy has been released, in the axial direction thereof, the energy of a low/intermediate-temperature fluid and a high-temperature, high-pressure fluid is converted into rotational motive power; this kind of radial turbine has widely been employed for recovering motive power from discharge energy discharged from various industrial plants in the form of a high-temperature, high-pressure fluid, for recovering exhaust heat from systems that gain motive power via a thermal cycle of a motive-power source or the like in a ship or a vehicle, and for recovering motive power in binary-cycle power generation in which a heat source having a low to intermediate temperature is utilized, such as geothermal power, OTEC, and so forth.
When various energy sources have a plurality of pressures, for example, as disclosed in Patent Literature (PTL) 1, a plurality of turbines, that is, one turbine for each pressure source, have been used. Alternatively, two turbine wheels are coaxially provided in some cases.
This is because radial turbines are designed to meet the optimal conditions for the respective pressures of the fluids. For example, the inlet radius R of a radial turbine is determined by the relationship g·H≈U2, where g is the gravitational acceleration, H is the head, and U is the inlet circumferential velocity of a turbine wheel. Specifically, assuming that the rotational speed of the turbine wheel is N (rpm), a value close to R≈U/2·π/(N/60) is set as the inlet radius R.
In addition, in a radial turbine that handles fluids having large flow-volume change, for example, as disclosed in Patent Literature 2, there is a known radial turbine in which a single inlet flow channel is divided by partitioning it with a partition wall. However, in this case, the size of the Inlet is changed in accordance with the flow volumes of fluids having the same pressure.
However, this is a case in which the fluids having the same pressure are handled by both inlet flow channels. In addition, because the two inlet flow channels are provided so as to be adjacent to each other simply by partitioning them with the partition wall, when handling fluids having different pressures, a high-pressure fluid leaks toward a low-pressure fluid, thus decreasing the turbine efficiency.